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Old 07-15-2009, 01:35 PM   #1
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Why do boxsters....

Why do boxsters drone with exhaust? I never have seen a explanation.

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Old 07-15-2009, 01:48 PM   #2
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What I was told...

...when I bought mine is that Porsche designed it that way. They installed less insulation in the body/cabin so that the exhaust note would be more prominent. It was Porsche's idea that true enthusiasts would appreciate (and expect) more vocal exhaust as part of the thrill of the drive. Hence, exhaust noise penetrates into the experience more.

I can't independently verify that, but it seems a reasonable explanation to me.

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Old 07-15-2009, 02:20 PM   #3
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Every car I've ever driven or rode in that had a louder aftermarket exhaust had noticeable drone and resonance. It's not just a boxster specific issue. Corsa is a well known exhaust manufacture that has a reputation for offering aggressive good souding exhausts with little drone, but they don't offer a model for Boxsters unfortunately.
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Old 07-15-2009, 02:26 PM   #4
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I have a modified factory muffler (ala Pedro type) and Fabspeed secondary bypass pipes. My car screams under accelation without any drone or resonance whilst cruising.
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Old 07-15-2009, 05:52 PM   #5
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All cars will drone at a certain rpm range... this is normally canceled out by the exhaust system... in a mid (or rear) engine car the length of the exhaust isnt long enough to damp the resonance out, especially with a lighter (most of the time shorter) aftermarket exhaust.
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Old 07-15-2009, 09:16 PM   #6
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Every exhaust has a resonant frequency. When the engine RPM matches the resonant frequency of the exhaust system, you get a huge increase in amplitude at that RPM range, which is what we hear as drone.

One of the reasons the piping diameter in factory exhausts is so small (in addition to all of the conspiracy theories about Porsche not wanting their low-end cars to compete with the 911) is to ensure the resonant frequency of the exhaust system falls outside the normal RPM range of the motor.

As you increase the piping diameter, remove baffles, and otherwise do things to improve airflow, you risk changing the resonant frequency of the exhaust to one that you will hit frequently while driving.
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Old 07-15-2009, 09:20 PM   #7
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Ever sit next to a crappy car at a light with a HUGE stereo system - and when a specific note hits, the whole car sounds like it's going to rattle apart? The music hits the resonant frequency of the speaker enclosure or the passenger cabin, and then the spoiler and shorty "euro" antenna fall off.

Quote:
Originally Posted by sd_boxster
As you increase the piping diameter, remove baffles, and otherwise do things to improve airflow, you risk changing the resonant frequency of the exhaust to one that you will hit frequently while driving.
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Old 07-16-2009, 07:13 AM   #8
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Quote:
Originally Posted by sd_boxster
Every exhaust has a resonant frequency. When the engine RPM matches the resonant frequency of the exhaust system, you get a huge increase in amplitude at that RPM range, which is what we hear as drone.

One of the reasons the piping diameter in factory exhausts is so small (in addition to all of the conspiracy theories about Porsche not wanting their low-end cars to compete with the 911) is to ensure the resonant frequency of the exhaust system falls outside the normal RPM range of the motor.

As you increase the piping diameter, remove baffles, and otherwise do things to improve airflow, you risk changing the resonant frequency of the exhaust to one that you will hit frequently while driving.
Bingo! Well said SD. A Porsche tuned exhaust system is very much like a trumpet or saxophone.

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